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<p>[QUOTE=&quot;cplradar, post: 1918298, member: 108985&quot;]Well, I researched this on the internet and found that they do use Potassium Cyanide</p><p><br /></p><p><a href="http://www.ncscoin.com/pdfs/conservation_guide.pdf" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.ncscoin.com/pdfs/conservation_guide.pdf" rel="nofollow">http://www.ncscoin.com/pdfs/conservation_guide.pdf</a></p><p><br /></p><p>Coins that exhibited normal tarnish were oftentimes</p><p>dipped into potassium cyanide to strip</p><p>away</p><p>their patina and leave</p><p>them bright. Even the United States Mint’s own curators would</p><p>periodically spruce up that institution’s collection with a rinsing in</p><p>cyanide, a risky business given this substance’s highly toxic nature.</p><p>In fact, the poisonous compound is known to have taken the life of</p><p>at least one prominent numismatist who, while engrossed in his</p><p>cleaning endeavors, mistook the deadly chemical for a nearby glass</p><p>of ginger ale. Fortunately, the use of cyanide to clean coins was</p><p>abandoned decades ago, and most of the pieces so treated have</p><p>naturally retoned to some degree.</p><p><br /></p><p>also</p><p><br /></p><p><a href="http://www.numismaster.com/ta/numis/Article.jsp?ArticleId=4580" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.numismaster.com/ta/numis/Article.jsp?ArticleId=4580" rel="nofollow">http://www.numismaster.com/ta/numis/Article.jsp?ArticleId=4580</a></p><p><br /></p><p>which this type of cleaning has been used to the detriment of the coins.</p><p><br /></p><p>Next, White discusses a cyanide coin dip. The association of cyanide with murder mysteries involving poison should be enough to turn any budding coin cleaner away from this technique. As White expresses it, &quot;cyanide dips contain poison that can lead to death if ingested. Also, if the dip is acidified it can produce hydrogen cyanide, a lethal gas.&quot; Isn&#039;t that what they use in the gas chamber for executions?</p><p><br /></p><p>In addition, I&#039;m reminded of Jim Jones and the mass suicide in Guyana by people drinking cyanide-laced grape Kool-Aid. Needless to say, I&#039;m not recommending a cyanide coin dip.</p><p><br /></p><p>Next, we have the ever-popular acid-thiourea dip. This is actually what people refer to when they talk about &quot;dipping&quot; a coin. Truth be told, almost any time you see a brilliant, untoned coin that you would expect to have a measure of toning because of its age, it has almost certainly been dipped. As Scott Travers, writing in The Coin Collector&#039;s Survival Manual (5th edition), puts it, &quot;It just isn&#039;t possible for 100-year-old silver coins to be as brilliant as when they were minted. Toning is a natural part of a coin&#039;s aging process.&quot;</p><p><br /></p><p><a href="http://www.coinbooks.org/esylum_v09n32a14.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.coinbooks.org/esylum_v09n32a14.html" rel="nofollow">http://www.coinbooks.org/esylum_v09n32a14.html</a></p><p>Cyanide is most effective in cleaning gold and other coins. Another</p><p>little known use of cyanide is in the electrolyte solution in making</p><p>coin and medal patterns -- galvanos -- these are oversize patterns</p><p>made from sculptors models intended to be reduced on a die-engraving</p><p>pantograph (as a Janvier) to cut a die or hub of appropriate size.</p><p><br /></p><p>Cyanide is ideal component in the electroforming baths for making</p><p>such copper galvanos. Such technology was developed by the French in</p><p>the Paris Mint and copied by other mints. I have yet to learn how</p><p>early it was in use in America (any E-Sylum reader know for certain?).</p><p>But it was well intrenched by 1920 for de Francisci&#039;s Peace dollar and</p><p>in use at the Philadelphia Mint for the next 40 years. [Copper galvanos</p><p>were ultimately replaced by an epoxy casting method that reduced the</p><p>time to make these patterns from days to hours.]</p><p><br /></p><p><a href="http://www.finishing.com/0000-0199/182.shtml" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.finishing.com/0000-0199/182.shtml" rel="nofollow">http://www.finishing.com/0000-0199/182.shtml</a></p><p><a href="http://www.mycoincollecting.com/collecting/cleaning-coins.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.mycoincollecting.com/collecting/cleaning-coins.html" rel="nofollow">http://www.mycoincollecting.com/collecting/cleaning-coins.html</a>[/QUOTE]</p><p><br /></p>

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